This invention relates to a power supply apparatus and, more particularly, to a power supply apparatus which may be used with, for example, an arc welder, a plasma arc welder, an arc cutter, a plasma arc cutter, a charger, and a plating apparatus.
Some power supply apparatuses provide DC current converted from AC current. Such apparatuses include components which generate a relatively large amount of heat during operation, and components which generate a relatively small amount of heat during operation. For simplification of description in this specification, the former components are referred to simply as heat-generating components, and the latter ones are referred to as less-heat-generating components. A power supply apparatus: including a group of heat-generating components and a group of less-heat-generating components disposed, being separated from each other, in a case has been proposed.
One such example is disclosed in U.S. Pat. No. 5,831,240 assigned to the same assignee as the present application. The power supply apparatus disclosed in this U.S. patent includes front and rear spaced-apart panels. A chassis divides the space defined by and between the front and rear panels into upper and lower spaces. Heat-generating components are disposed in the lower space, and less-heat-generating components are disposed in the upper space. A semiconductor module, which is a heat-generating component, is disposed in the upper space, too. The semiconductor module, however, is mounted on a heat sink. The heat sink extends through the chassis into the lower space. Accordingly, the heat generated by the semiconductor module is effectively released into the lower space. A fan is disposed in association with the lower space for expelling the heat out of the case. The semiconductor module contains all of the semiconductor devices used in the power supply apparatus. Above and near to the semiconductor module, disposed is a printed circuit board containing a control circuit for controlling those semiconductor devices which need to be controlled. The upper and lower spaces are closed by left and right side panels each having a U-shaped cross-section, whose edges are brought to abut each other.
Since the chassis is joined to the front and rear panels, the internal components and structure can be inspected only with the chassis kept joined to the front and rear panels, which makes it difficult to inspect and repair those components which are disposed near the front and rear panels. Also, for replacing the semiconductor module with a new one, it is necessary to first remove the left and right side panels and dismount the printed circuit board disposed above the semiconductor module before replacement. It, therefore, takes a relatively long time to inspect and maintain the power supply apparatus.
An object of the present invention is to provide a power supply apparatus which can be inspected and maintained with ease.
A power supply apparatus according to the present invention has first and second spaced apart chassis, which may preferably be formed of thin members, e.g. plate-like members. A heat sink is disposed between the first and second chassis, and the first and second chassis are mounted to the heat sink. A printed circuit board is detachably mounted to at least one of said first and second chassis on the surface opposite to the surface by which the chassis is mounted to the heat sink. The printed circuit board is preferably spaced from the heat sink. A semiconductor module is mounted on the surface of the heat sink facing toward the printed circuit board. The semiconductor module is electrically connected to the printed circuit board to form a power supply circuit. The heat sink, the first and second chassis, and the printed circuit board form an assembly, of which lateral sides are covered by a hull. Either a single-unit type hull or a split type hull can be used. The front and rear ends of the assembly, i.e. the front and rear ends of the first and second chassis, respectively, are covered by the front and rear panels. It should be noted that the assembly are separable from the front and rear panels.
Since the first and second chassis are mounted to the heat sink, they are mechanically separated from the front and rear panels which are located in the front and rear of the heat sink. With this arrangement, components disposed near the front and rear edges of the first and second chassis can be inspected and maintained without difficulty. In addition, since the printed circuit board can be easily removed from the chassis so as to expose the semiconductor module, inspection, maintenance or replacement of the semiconductor module is easy.
A window may be formed in the said at least one of said first and second chassis. The semiconductor module is disposed to protrude through the window toward the printed circuit board, whereby, when the printed circuit board is removed, the semiconductor module is exposed through the window, which facilitates inspection and maintenance of the semiconductor module.
The semiconductor module may be connected with a detachably connector to the printed circuit board, so that the printed circuit board can be readily removed.
The heat sink may be formed of two halves, which are preferably of the same shape. The two heat sink halves have a plurality of fins on their mating sides. Since the heat sink is formed of two halves, it can be easily manufactured. A heat sink may have fins which extend substantially horizontally and are vertically spaced. A single-unit type heat sink with such structure formed by drawing cannot have a large ratio of the length of the fins to the spacing between adjacent fins cannot be made large. In contrast, if such heat sink is formed from two halves with fins having abutting tip edges, the heat sink as a whole can have a large fin length-to-spacing ratio. If the heat sink is formed of two halves having the same shape and size, its manufacturing is also simplified.
A blower may be disposed between corresponding ends of the first and second chassis to thereby cool the heat sink. Since the heat sink is interposed between the first and second chassis, the chassis and the heat sink effectively provide a duct for air flow formed by the blower, so that the heat sink can be cooled efficiently.
The power supply circuit may include a transformer. The transformer is disposed beneath the heat sink and has portions thereof extending through the first and second chassis. Sometimes, a power supply circuit is provided with a transformer disposed between input and output sides of the circuit. According to the present invention, disposing the transformer beneath the heat sink can eliminate need for providing a space dedicated for the transformer. In addition, the transformer can be supported by the first and second chassis, no dedicated support for the transformer is required.
The transformer may be a thin or small-thickness transformer, requiring a smaller space in the power supply apparatus, which results in downsizing of the power supply apparatus. The thin transformer may include conductors formed of laminated thin conductor sheets with insulating sheets disposed between adjacent ones of the conductor sheets. The thin conductor sheet may be formed by cutting a metal conductor sheet into a loop-shape.
Two printed circuit boards may be used. A first one of the printed circuit board is detachably mounted to the first chassis, and the second printed circuit board is detachably mounted to the second chassis. The first printed circuit board includes an input side circuit portion of the power supply circuit, and the second printed circuit board includes an output side circuit portion of the power supply circuit. Separate semiconductor modules are used for the input and output side portions of the power supply circuit. The semiconductor module for the input side circuit portion is disposed on the surface of the heat sink facing toward the first chassis and extends to protrude through the first chassis toward the first printed circuit board, whereas the semiconductor module for the output circuit portion is disposed on the surface of the heat sink facing the second chassis and extends through the second chassis toward the second printed circuit board. With this arrangement, in order to inspect the semiconductor module for the input side circuit portion, the first printed circuit board only needs to be removed, and, similarly, in order to inspect the semiconductor module for the output side circuit portion, only the second printed circuit board needs to be removed. In addition, the protrusion of the semiconductor modules through the first and second chassis toward the respective printed circuit boards facilitates inspection and maintenance of the semiconductor modules.
A thin transformer may be provided between input and output side circuit portions of the power supply circuit. The transformer is disposed beneath the heat sink. The input side of the transformer is connected to the first printed circuit board, and the output side of the transformer is connected to the second printed circuit board. This arrangement requires a smaller space for the transformer, resulting in downsizing of the power supply apparatus, and also requires shortest wiring for the input and output sides of the transformer.